99 5.0 Misfires when warmed up

[Mbrooks420]

For the oil leak check the rear main seal, it's fairly common on the 5.0s

 

[Sedare]

For the oil leak check the rear main seal, it's fairly common on the 5.0s

Its losing oil somewhere above the driver side strut tower, but it is also losing a little bit above the water pump near the intake manifold. Its an odd spot, but nothing about this car matches what I have found for common issues. the guy that owned it before me was an AmsOil vendor, and maintained it religiously, and I am the 2nd owner. (except for the 4th wire on the plug wireset evidently. lol)

 

[CDW6212R]

The oil leakage is not common but not rare either. Some won't leak at all for 200k miles(my Mercury is at 206k), and my 98 I bought leaked from several places, plus eats it. Try snugging all of the bolts for the intake, oil pan, and timing cover as you can reach them. The gaskets are pretty good, which is why the rear and front seals are more common to have leakage. I've tried a couple of seal restorer products, but my leaks are tiny compared to what's missing every 2-3 weeks. Rough maintenance helps to make an engine eat oil a lot. You hope you find a good one well taken care of, like with Amsoil etc.

 

[Sedare]

Crap, I was wrong. Problem is still here, I just didn't drive it enough yesterday. Ill still get that 4th wire replaced, but I think I'm going to get my laptop setup to do a live diagnostic.

 

[Turdle]

I'd have replaced that wire 3 days ago!

You do not have to worry about routing it like ford did, but you do need to keep it away from the exhaust manifold and the egr tube. Push the spark plug end down where you want it to go, zip ties are your friend here.

 

[Sedare]

It just sucks that I'm back to square one. Ill get that last wire no problem. Now I am debating if it's either fuel issues, coil pack systems, or a head gasket leak? I'll do the fuel filter this week.

 

[CDW6212R]

Do you have any other coil pack to test with? The 302 uses the same unit as all 4.6 engines that had them. I had a bad coil pack which was not very old(Accel), and had changed a bunch of other things first knowing it couldn't be the coil. If you can get one, test that also, the miss may or may not be pairs of cylinders from a coil pack.

 

[Sedare]

Ill.go to a local you pull it and grab a set

 

[1998Exp]

Don't know about the 95, but on later V8 engines, the #3 and #4 wires are the most affected by exhaust manifold heat, and have shields on them to help. If the situation with the tubular manifold on the OP's engine is anything similar, that most neglected #4 wire is also the one in the worst condition. The usual failure mode is arcing through a crack or pinhole in the insulation to something metallic in the vicinity.
Edit: misread the OP's model as 95. 99 has the cast manifold, with heat-shielded #3 and #4 wires. Still, these shields are not very effective. The #4 wire on my 98 failed at least twice. When it fails, you still have spark, but it's weak. The easiest way to positively diagnose that is with an oscilloscope. Otherwise, substitution is the way to go.

 

[Sedare]

Don't know about the 95, but on later V8 engines, the #3 and #4 wires are the most affected by exhaust manifold heat, and have shields on them to help. If the situation with the tubular manifold on the OP's engine is anything similar, that most neglected #4 wire is also the one in the worst condition. The usual failure mode is arcing through a crack or pinhole in the insulation to something metallic in the vicinity.

That makes sense that the wire for number 4 has the longest heat shroud. Mine is a 99 not a 95, so it could be later enough to fit what you are saying.

 

[J_C]

It just sucks that I'm back to square one. Ill get that last wire no problem. Now I am debating if it's either fuel issues, coil pack systems, or a head gasket leak? I'll do the fuel filter this week.

One thing at a time. You're only hurting your progress and making the topic unfollowable by going back and forth like this. Do the wires. `100% finish that and confirm all deliver spark. Nothing more. Completely rule out each subsystem one at a time.

 

[Sedare]

One thing at a time. You're only hurting your progress and making the topic unfollowable by going back and forth like this. Do the wires. `100% finish that and confirm all deliver spark. Nothing more. Completely rule out each subsystem one at a time.

Due to the check engine codes this effectively DOES rule out the plug wires. A faulty 4th wire will not cause a misfire on 2 5 & 6, while not causing a misfire on 4. Sorry, but this is just trouble shooting. Had nothing to do with misleading repairs.

You are right on doing them 100%. Thankfully my head cold is going away tonight, and ill get to it first thing AM.

 

[delexploder]

My number 4 is run under the intake elbow and zip tied to the ac line, keeps it off my egr tube ,

 

[Sedare]

Ok swapped the 4th wire...
Nothing changed as I expected.

More trouble shooting took place with my brother in law (good with cars) and he helped with the 4th wire.

When we finished it was missing on one cylinder entirely. Turns out the was no spark at all coming from the coil pack for wire 1.

Then the odd part. I shut it off and on again and the spark worked again, and I was back to my intermittent cylinder misfire.

Should I go ahead and replaced my coil packs, or is that a sign of another issue?

 

[1998Exp]

These random misfires make me suspect the grounding of the coil packs. They ground through the mounting bracket. Before replacing, I would remove the packs and inspect/clean the contact surface there.

 

[CDW6212R]

The engines with coil packs are waste spark systems, two cylinders fire each time. So while the #1 plug fires, so does the #6 plug. That should make it logical to track misfires, but not always. It should mean that the coil is okay since the #6 plug should also have an issue. What have the CEL codes been as you have worked on the plugs and wires, which are just guides to help locate the problem.

Checking the grounds, power, as well as the main connectors for the coils, and PCM etc, is good to do again while hunting ignition troubles.

 

[Sedare]

I will stop by and check/clear codes after work tomorrow.

 

[MAS Tequila]

I've been chasing the same shadow of a miss for a couple of months now.

Mine has gotten worse.


It's to the point where it appears to be the harmonic balance.


I have a new one coming, it should be here by Thursday.

When it's cold, it's smooth, but as it heats up it gets worse.

 

[Sedare]

What is involved in changing a harmonic balancer

 

[J_C]

These random misfires make me suspect the grounding of the coil packs. They ground through the mounting bracket. Before replacing, I would remove the packs and inspect/clean the contact surface there.

Is it random now? Looked like cyl. 1. If a grounding problem then I would suspect all would get random misfires, except I still don't agree that the coil pack needs any ground through the bracket. Its electrical function is handled by the wiring. It has 3 pins (on each of the two, twin coil packs for an 8 cylinder, or 4 pins for the 3 coil packs for a 6 cyl).

One pin is 12V input, then the other two are grounds through the ECM for each coil in the pack. It depends on only having ground through the ECM to trigger it. Grounding the electrical portion of the circuit through the mount would prevent it from working, but the mount is just the stacked metal core plates, insulated from the coil windings.